[bugfix] generate_user_files: set main_family & main_code
[bugfix] generate_user_files: set main_family & main_code

main_family & main_code have not been changed after initializing
their default value, even if the user has chosen other values.

Bug: T195602
Change-Id: I36a5764e1fe49c7eccbcfd18f5c71368c8eeb342

wikimedia/pywikibot-core,wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core